The present project is concerned with the question of interoceptive (visceral) influences on neuronal activity of the forebrain. In an earlier microelectrode study on awake, sitting squirrel monkeys, it was shown that vagal volleys reset the respiratory cycle and entrained units in certain structures of the forebrain to discharge in phase with respiration. A subsequent study in which the start of the expiratory phase was used to time the beginning of recordings revealed that about 10 percent of neurons in certain parts of the forebrain discharge in phase with respiration. In addition to obtaining more information about the distribution and incidence of such units, it was the purpose of the present study to learn whether or not their phasic discharge was related to inputs from the olfactory nerves. It was found that the respiratory-related phasic unit activity could be recorded following the destruction of the olfactory nerves.